Polonium
Halos in Primordial Rock Prove the Earth is Young

In the early 1970's Robert Gentry's published some information about Polonium
halos in primordial granite. Since polonium has a half life of a few minutes,
the results seemed to indicate an almost instant creation of primordial rocks.
Such an interpretation would be incompatible with the relatively slow formation
of the earth from a swirling cloud of dust and gas.

However, later work showed that Gentry made numerous errors about the geology
of where the halos were found. In fact, Gentry's samples came from postmagmatic
hydrothermal fluids that were deposited in dykes between the granite. In fact,
Gentry had not even sampled the oldest rocks available (from the Superior
Province of Archean age in northern Ontario) but had acquired his samples from
the much younger Grenville Province. In addition to this, it appears that
Gentry's halos were not from polonium, but most likely from other radioactive
elements that have a longer half life. For all the details, check the link
below, which was published in the May 1988 Issue of the Journal of Geological
Education.